Genetic architecture facilitates then constrains adaptation in a host–parasite coevolutionary arms race

Abstract

Significance Validating an almost century-old hypothesis, we show that a critical host-specific adaptation in a brood-parasitic bird, mimicry of host egg coloration, is maternally inherited, allowing mothers to transmit specialized mimicry to their daughters irrespective of the father’s host species. This genetic architecture, however, is a double-edged sword for parasites: the loss of recombination and heterozygosity as sources of evolutionary novelty likely constrains the parasite from mimicking the full range of color polymorphisms that hosts have evolved as an escalated defense against parasitism. This important tradeoff of asexual inheritance may have relevance for understanding coevolution in other host–parasite systems.